Lens barrel standard position detection device and method

Abstract

A lens barrel standard position detection device, attached to a lens barrel equipped with a fixed tube having a first member and a movable tube rotationally moving back and forth along an optical axis of the lens barrel and having a second member engaging the first member of the fixed tube, to detect when the movable tube reaches a predetermined standard position. The lens barrel standard position detection device includes an actuating element movable between a first position and a second position, the actuating element moving to the second position when a working plane portion of the second member moves into contact with the actuating element corresponding to the movable tube reaching the predetermined standard position along the optical axis, an urging member which maintains the actuating element in the first position in a normal state due to an urging force of the urging member, and a detection unit which detects when the actuating element moves to the second position which opposes the urging force of the urging member, thereby detecting the movable tube reaching the predetermined standard position.

What is claimed is: 
     
       1. A camera lens barrel comprising: a fixed tube integrally fixed to said camera and having a first member on an inner circumferential portion of said fixed tube;   a movable tube which rotationally moves in said back and forth direction along said optical axis said movable tube having a second member on an outer circumferential portion of said movable tube which engages said first member of said fixed tube; and   a lens barrel standard position detection device, arranged on an outer circumferential portion of said fixed tube, to detect when said movable tube moves to a predetermined standard position on said optical axis by detecting a state of the second member.   
     
     
       2. The camera according to claim 1, wherein said second member is a male helicoid member and includes a crest having a working plane portion which actuates said lens barrel standard position detection device when said movable tube moves to said predetermined standard position. 
     
     
       3. The camera according to claim 2, wherein said lens barrel standard position detection device includes: an actuating element movable between a first position and a second position, said actuating element moving to said second position when said working plane portion of said crest moves into contact with said actuating element corresponding to said movable tube reaching said predetermined standard position;   an urging member which maintains said actuating element in said first position in a normal state due to an urging force of said urging member; and   a detection unit which detects when said actuating element moves to said second position which opposes said urging force of said urging member.   
     
     
       4. The camera according to claim 3, wherein an end portion of said actuating element is disposed in a trough of said first member, which is a female helicoid member, of said fixed tube and comes into contact with said working plane portion of said crest of said male helicoid member of said movable tube when said movable tube reaches said predetermined standard position. 
     
     
       5. The camera according to claim 3, wherein said detection unit is disposed on said outer circumferential portion of said fixed tube. 
     
     
       6. The camera according to claim 3, wherein said detection unit is a switch having contact terminals which separate to turn said switch OFF when said actuating element moves to said second position. 
     
     
       7. The camera according to claim 2, wherein said working plane portion of said crest is a sloping surface inclined at an angle with respect to an advancing direction of said crest of said male helicoid member of said movable tube along said optical axis. 
     
     
       8. The camera according to claim 2, wherein said working plane portion of said crest is a surface parallel to said optical axis. 
     
     
       9. The camera according to claim 1, wherein said predetermined standard position is located between a wide angle position of said zoom type lens barrel and a retracted position of said zoom type lens barrel. 
     
     
       10. A camera as recited in claim 1, wherein the lens barrel is a zoom type lens barrel for telephoto and wide angle photography, which zoom type lens barrel extends from and retracts into a body of said camera in a back and forth direction along an optical axis of said zoom type lens barrel. 
     
     
       11. A camera as recited in claim 10, wherein the fixed tube is integrally fixed to a frame in said camera body. 
     
     
       12. A lens barrel standard position detection device, attached to a lens barrel equipped with a fixed tube having a first member and a movable tube rotationally moving back and forth along an optical axis of said lens barrel and having a second member engaging said first member of said fixed tube, said lens barrel standard position detection device comprising: an actuating element movable between a first position and a second position, said actuating element moving to said second position when a working plane portion of said second member moves into contact with said actuating element corresponding to said movable tube reaching a predetermined standard position along said optical axis;   an urging member which maintains said actuating element in said first position due to an urging force of said urging member; and   a detection unit which detects when said actuating element moves to said second position which opposes said urging force of said urging member, thereby detecting said movable tube reaching said predetermined standard position.   
     
     
       13. The device according to claim 12, wherein an end portion of said actuating element is disposed in a trough of said first member of said fixed tube and comes into contact with said working plane portion of said second member of said movable tube when said movable tube reaches said predetermined standard position. 
     
     
       14. The device according to claim 13, wherein said detection unit is disposed on an outer circumferential portion of said fixed tube. 
     
     
       15. The device according to claim 12, wherein said working plane portion is a sloping surface inclined at an angle with respect to an advancing direction of said second member of said movable tube along said optical axis. 
     
     
       16. The device according to claim 12, wherein said working plane portion is a surface approximately parallel to said optical axis. 
     
     
       17. The device according to claim 12, wherein said detection unit is a switch having contact terminals which separate to turn said switch OFF when said actuating element moves to said second position. 
     
     
       18. A method of detecting when a movable tube of a zoom type lens barrel reaches a predetermined standard position on an optical axis of said zoom type lens, comprising the steps of: urging an actuating element to remain in a first position due to an urging force;   moving a movable tube having a second member with a working plane portion back and forth along said optical axis;   moving said working plane portion into contact with said actuating element when said movable tube reaches said predetermined standard position;   moving said actuating element to a second position opposing said urging force when said working plane portion contacts said actuating element at said predetermined standard position; and   detecting when said actuating element moves to said second position.   
     
     
       19. The method according to claim 18, wherein said detecting step includes the step of separating contact terminals of a switch to turn said switch OFF when said actuating element moves to said second position. 
     
     
       20. The method according to claim 19, further comprising the steps of: providing an end portion of said actuating element in a trough of a first member of a fixed tube of said zoom type lens barrel;   engaging said first member of said fixed tube with said second member of said movable tube;   providing said switch on an outer circumferential portion of said fixed tube; and   moving said working plane portion of said second member into contact with said end portion of said actuating element.